U.S. Patent Application No. 2004101172 (Lane) discloses a finger imaging system for receiving the finger of a person being fingerprinted by an automated fingerprint reader. The system includes a finger imaging device having a finger receiving portion for receiving the finger to be fingerprinted. Extending outward from the finger receiving surface is a locator bar that engages a skin crease of the subject finger when it is in about in the desired position. U.S. Patent Application 2004101171 (Lane et al.) discloses a finger imaging system for receiving and holding a finger of a person being fingerprinted by an automated fingerprint reader. The system includes a finger imaging device having a finger receiving portion and a finger positioning portion, together forming a recess of reducing dimension such that a subject finger forcibly inserted into it is held in a stable position. And finally, U.S. Patent Application No. US2004076314 (Cheng) discloses an apparatus that includes a fingerprint sensor and a guiding means. The sensing site of the fingerprint sensor makes a relative and obtuse angle with a guiding plane of the guiding means.
Traditionally, in order to record a fingerprint, ink was applied to a finger and then the finger was “rolled” across a paper or other ink receptive surface to print an image of the fingerprint. Fingerprints left by touching a surface and leaving oil residue are captured forensically by a variety of process techniques that “lift” and reveal the fingerprint.
In more recent years, alternative technologies have been developed that can reveal the fine features within a fingerprint and capture the fingerprint directly from the finger or from the living tissue under the surface of the finger skin which grows outward to become the finger minutiae. Electronic sensing technology involves holding the finger on a sensing system as the system detects skin or tissue differences across the finger area or just a portion of the finger area in order to reveal an image of the print or in order to create an electronic representation of the fingerprint, for example as a digital file. Examples include optical scanners, electroluminescent pressure sensitive systems, integrated circuits with the ability to measure individual pixel sized capacitance, and more.
The production cost for some types of fingerprint scanning systems is driven by the size of the finger area to be sensed. This is especially true for silicon based or integrated circuit (IC) type sensors. Like most IC's, the larger the IC, the more costly it is to produce assuming equal device geometries and layer counts. The production cost of the sensor is directly related to the sensing area, and mass production of sensors the size of a thumb is not optimal when only a relevant portion of a finger needs to be scanned in order to build a fingerprint authentication system. If just a relevant portion of the print is to be used in order to reduce system cost, then it becomes important to place nearly the same relevant portion of the finger that was originally enrolled upon the sensor for every authentication or identification event.
Clearly a smaller sensor would cost less and, assuming the relevant area of the finger sensed is still necessarily large enough to provide an acceptable matching capability or security level, then the optimal solution would be this smaller sensor, leaving out significant portions of the total fingerprint area. The finger guide device of the present invention is a device which may be used to reliably reposition a finger upon a small sensor to enable more efficient identification. The device reduces false rejects caused by failure to position the finger close enough to its original enrollment position or positions. The finger guide device assures that the sensor can read matching relevant portions of the fingerprint, which is to stipulate reading generally the same relevant portions as those captured and stored in a template used for comparison and matching. The finger guide device reduces the incidence of false rejects by naturally (for example, comfortably or intuitively) and non-forcibly guiding the subject finger to approximately (generally) the same and original enrollment position each time the fingerprint identification system is used.
When smaller sensors are used, if the finger is enrolled in a manner that scans one relevant portion of the finger, or perhaps several overlapping portions of the finger's print area which are then electronically assembled by a computer into a completed “template” representing a larger portion of the original subject's fingerprint than any single scan could produce alone, then the system depends upon the subject user being able to touch the sensor consistently in the same approximate place so that a matching relevant portion of the finger is read by the sensor so that accurate authentication may take place. Failure to replace the finger accurately in generally the same location causes false rejects; or, in other words, because the sensor sees a different and irrelevant area of the finger then it can not match with the data from previously enrolled relevant fingerprint portions in the template, and it rejects a known acceptable subject user. This is a false reject. If the system permits additional attempts, and if the second or subsequent try finally aligns the minutiae containing a relevant portion of the fingerprint matching a portion originally stored during enrollment, the subject will then be accepted (identified or “authenticated”). The finger guide device reduces the average number of attempts to authenticate known subjects by providing a simple, generally oval or rectangular funnel like guide for the finger that physically encourages the finger into the correct position and provides a variety of tactile feedback means for the subject user in order to make it easier to “find” the right position again, even after substantial time has passed between enrollment and the next authentication event. In contrast, with basic flat surface sensors or sensors surrounded by generally flat surfaces or even poorly designed sensors, this false reject rate for untrained subjects can range from ten to fifteen percent of all attempts, or even higher with different system settings.